Since the advent of credit cards in the 1920s, various types of personal cards (e.g., cash cards, identification cards, shopping cards, credit cards, etc.) have been widely used for performing various transactions. Recently, IC cards have become very popular due to the many advantages offered by IC cards including, for example, convenience, security, and various types of utility functions that are enabled by use of IC cards.
Typically, an IC card is fabricated with a thin semiconductor device attached on a credit card-sized plastic sheet with thickness of about 0.5 mm in the form of chip-on-board (COB). An IC card is highly adaptable for use with advanced information multimedia applications because IC cards provide better security and protection from data loss, as compared to cards having magnetic tapes.
In general, for IC cards having similar patterns and sizes of typical magnetic strip cards, there are two types of IC cards, i.e., contactless IC cards (CICC) and remote coupling communication cards (RCCC). A CICC (as developed by AT&T) is capable of sensing in the range of ½ inch, and the RCCC can be sensible in the range of 700 cm, which is standardized as ISO DIS 10536.
There is another way of classifying IC cards based on, e.g., whether the IC card comprises an embedded microprocessor. An IC card having an embedded microprocessor is generally referred to as a “smart card”, which is distinguished from contactless IC cards and memory cards which do not include microprocessors. A smart card typically comprises a central processor unit, an electrically erasable and programmable read-only-memory (EEPROM) for storing application program files, a ROM, and a RAM.
Smart cards can be used in various applications, providing high reliability/security, large capacity for data storage, and various functions (e.g., electronic purse). Indeed, smart cards can be utilized in various fields to facilitate managing information with bi-directional communication, distributed processing, and secured information preservation. Such fields include, e.g., finance, distribution, factory and office automation, medical treatment, traffic, industries, social security, mobile communication, pay phones, cable televisions, maintenance for power, gas, and water supply, education, credit cards, debit cards, pre-paid cards, city gas maintenance, information security, and home banking. Correspondingly, given the current trend of integrating various functions associated with a service in a single card, smart cards conveniently provide the apparatus and communication methods that are needed for supporting various services.
It is preferable for smart cards to provide reliable security that is capable of maintaining information stored therein so as to prevent the outflow of information for users or system managers. Some methods for monitoring internal signals of smart cards to find data features may cause damage to the data, for example, using an oscilloscope for scanning metal lines on a chip surface after removing a silicon oxide layer covering the chip surface (called “de-capsulation”). To eliminate such monitoring, a detection device is needed for detecting a de-capsulation event, such as a light exposure detector coupled to an optical receiver, or a passivation removal detector. Another way of monitoring a smart card is to monitor data that is being communicated through transmission lines using a frequency detector to determine if a main clock signal frequency is out of a predetermined range.
A smart card should be adapted to protect against physical damage due to, e.g., operation environments and unauthorized de-capsulations. A voltage detector can be employed to protect a smart card by managing a range of a standard voltage and protect against over-ranging of the standard voltage, which may cause destructive electrical stress on the smart card. Further, a temperature sensor is useful to detect abnormal temperatures to prevent against damage to the smart card due to abnormal low or high temperatures.
As described above, a conventional smart card can be protected from damage, e.g., information leakage by external intrusions, physical destruction, data modulation, or abnormal environments of operation, by resetting internal circuits of the smart card as well as a microprocessor, when there is at least a valid detection signal generated from a detection device (i.e., optical detector, passivation removal detector, frequency detector, voltage detector, temperature sensor, etc.). Conventional smart cards, however, do not include functions that enable a user to acknowledge unauthorized intrusions or reset reasons while a smart card is being conductive with re-encapsulation after its recovery of main clock frequency, voltage, environmental temperature, and so on. In fact, even if private information about a personal affair or a financial account has been stolen or modified by a malicious intruder, an authorized user or a permitted system manager could not determine or verify an illegal trespass.